#! /bin/bash

val=`expr 2 + 2`
echo "两数之和为：$val";

a=10
b=20

val=`expr $a + $b`
echo "a + b = $val";

if [ $a == $b ]
then
  echo "a等于b";
else
  echo "a不等于b";
fi

if [ $a -eq $b ]
then 
  echo "$a -eq $b : a 等于 b";
else
  echo "$a -eq $b : a 不等于 b";
fi

